Particle advancing apparatus



March 17, 1959 L. A. CARLSMITH ETAL 2,

PARTICLE ADVANCING APPARATUS Filed June 29. 1956 2 Sheets-Sheet 1 March1 L. A. CARLSMITH ETAL 2,

PARTICLE ADVANCING APPARATUS Filed June 29, 1956 2 Sheets=-$heet 2.

PARTICLE ADVANCING APPARATUS Lawrence Allan Carlsmith, Amherst, and JohnP. Rich, Nashua, N. 1-1., assignors to Improved Machinery, Inc., Nashua,N. H., a corporation of Maine Application June 29, 1956, Serial No.594,791

2 Claims. (Cl. 92-7) This invention relates to the continuous pulping offibrous material, and is a continuation-in-part of our copending U. S.application for Letters Patent, Serial No. 561,405, filed January 26,1956. More particularly, the present invention relates to improvementsin the novel apparatus and methods for advancing the solid particles ofa solid-liquid mixture through said liquid independently of the movementof the liquid as described in said earlier application and dominated bycertain of the claims thereof, although not specifically shown anddescribed therein.

Pulping of wood or other fibrous material is carried out, for example,by digesting particles of fibrous materials such as wood chips in ahighly heated liquid chemical solution preferably under pressure, as inthe well known soda or sulfate processes for the manufacture of paperpulp. As another example, the digestion may also be carried out bysteeping the fibrous materials at atmospheric or sub-atmosphericpressure in cold liquid chemical solutions such as nitric acid orcaustic. At the present time, such digestion in either case is usuallycarried out in batches, that is, a digester is filled with the rawmaterial, such as wood chips, after which the chemical digester solutionis admitted and suitable reaction conditions maintained for an intervalof time sufficient to digest the wood chips. Thereafter, the batch ofchips is discharged.

One of the major problems which must be solved in order to provide acontinuous pulping process which would consist in continuously feedingthe solid raw material, such as wood chips, into one end of theapparatus used for the digestion, and causing such raw material to movethrough said apparatus while admitting the heated chemical digestersolution and finally discharging the material from the other end of theapparatus in the form of pulp, arises from the nature of the reactingmixture itself, that is, the mixture of discrete particles in a liquid.It has proved to be most difficult to control the movement of suchparticles into a reacting vessel and through the liquid solution ofchemicals to an outlet at the other end of the apparatus, since theparticles are subject to both sticking and channeling which prevents theuniform movement essential for the production of pulp having uniformcharacteristics. Further difficulty arises in controlling the movementof the liquid, since it freely drains away from the mass of solidparticles, making it impossible to use the liquid as a vehicle forcarrying the solid particles through the apparatus.

Still another problem arises from the tendency of the solid particles toplug up strainers and the like used to separate the solid particles fromthe liquid, particularly when they are mounted in an enclosedcontinuously operating system.

According to the present invention, we have provided a novel apparatusfor advancing the solid particles, such as wood chips, of a solid-liquidmixture through said.

liquid at a rate of movement substantially independent of the rate ofmovement of the liquid, and without stickice ing or channeling of saidparticles, as well as novel-means and methods for compacting such solidparticles and for causing limited reciprocatory relative movementbetween the solid particles and the liquid. I

It is a feature of the invention that it is particularly adapted to aidin feeding solid particles suspended in a liquid into a reaction vessel,as well as for thereafter advancing such particles upwardly through suchreaction vessel at a uniform rate to discharge at the other end thereof.

It is another feature of the invention that it is selfcleaning inoperation, so that plugging difiiculties do not arise even withcontinuously operating systems.

For the purpose of more fully explaining a preferred embodiment of theinvention, reference is now made to the following specification,together with the accompanying drawings, wherein:

Fig. 1 is a diagrammatic view of a continuous pulping apparatusemploying the particle advancing means of this invention;

Figs. 2 and 3 are enlarged cross-sectional elevations showing at twodifferent stages of operation a portion of the apparatus of Fig. 1having therein the particle advancing means of ths invention;

Fig. 4 is a cross-sectional elevation of a portion of the means of Fig.l; and

Fig. 5 is an isometric view showing a portion of the means of Figs. 2and 3.

Referring to the drawings, in Fig. 1 is shown a complete continuouspulping apparatus including a mixing means for suitably mixing andimpregnating fibrous material such as wood chips with a liquid chemicalsolution such as a solution of soda ash to provide a solidparticleliquid mixture or slurry. Such mixture is then fed underpressure through an opening in the wall of an upright pressurizedreaction vessel of upwardly increasing crosssectional area wherein thechips are treated by heating them under pressure in said solution asthey are moved upwardly therethrough until they are discharged as adigested slurry at the top of the reaction vessel. Novel foraminouspiston means mounted adjacent the entrance end of the vessel andextending throughout substantially the entire horizontal cross-sectionalarea thereof adjacent the entrance end of said vessel closely adjacentthe inner wall of said vessel are provided for advancing and compactingthe chips or other solid particle component of the solid particle-liquidmixture in an'elongate'd mass or zone extending throughout the majorportion of the length of the elongated pressurized reaction vessel at arate substantially independent of the rate of movement of said liquid,the feeding of said mixture through the wall of the vessel preferablytaking place in timed relationship to the piston adjacent to theadvancing face thereof. 7 Thus, the solid particle-liquid mixture,because of the free movement of liquid through the piston means, may befed into the reaction vessel, the mass of chips advanced therethroughthrough said zone at a uniform average rate without sticking orchanneling and the digested chips then discharged to so provide uniformdigestion as well as to provide control of the degree of digestion bycontrolling the rate of advance. Since such rate of advanceissubstantially independent of the rate of movement of the liquidcomponent of the solid particle-liquid mixture, the liquid may berecirculated for heating it as desired. Additionally, the chip advancingmeans may also act to cause a limited reciprocatory relative movementbetween the solid particles and the liquid, or additional means'thereformay be providedif desired.

In more detail, the mixing or impregnating portion of the apparatusincludes a tank 12 filled with a suitable liquid chemical solution, anda hopper 14 containing chips or other fibrous materials. A centrifugalpump 16 with the rotor 19 of the valve 18 in one position, the bore 20of said rotor receives a charge of chips from hopper 14, the chips beingkept from passing outwardly from said bore through exhaust pipe 21 by ascreen 22 at the opposite end thereof, and in the other position feedssaid charge together with a charge of liquid from pump 16 which passesthrough screen 22 to inject a mixture of chips and liquid into thepressurized reaction vessel 24 through an opening 25 therein. Othertypes of intermittent feeding means may be used. For example, acentrifugal or other non-positive displacement pump may be used eitherwith a suitable gate valve timed with the piston or with the pistonitself used as a valve by positioning the inlet within the piston strokeso as to be closed when the piston is advanced. Under somecircumstances, continuous feed, as by a twin intermeshing screw feeder,may be used.

The generally cylindrical upright elongated pressure vessel 24 ofgenerally uniform cross-sectional area at least not decreasing in itsupward direction comprises the reaction portion of the apparatus andincludes a top discharge mechanism 26 connected to a suitable pulpstorage tank (not shown). It is important that vessel 24 although ofgenerally uniform cross-sectional area have a slight taper to provide agradually increasing cross-sectional area, a taper of about inch ofdiameter per foot of length, for example, being suitable. A filtersection 28 as well as a bottom outlet 29 may be provided in said vessel24 for recirculation of the liquid component to heat it as desired. Anysuitable heating means may be employed, for example, steam may beinjected into the liquid, to heat it.

As best shown in Figs. 2 through 4,the novel advancing means includes aforaminous piston means mounted for reciprocatory movement through alimited distance relatively to the length of the vessel 24 within thereaction vessel 24 near the lower end thereof by means of a shaft 30extending vertically through the bottom of said vessel generally axiallythereof. More specifically, said foraminous piston means comprises acircular plate 32 having therein a plurality of perforations 34preferably extending over its entire surface and sufi'icient in numberto allow substantially free passage of the liquid there through but ofsmall enough size to prevent passage of the chips or other fibrousmaterial. Furthermore, the peripheral edge thereof is positioned closelyadjacent the inner walls of the reaction vessel 24 so that passage ofchips into the bottom portion of said reaction vessel 24 may beprevented.

For feeding the pressurized mixture of chips and liquid to the uppersurface of said piston, the opening 25 is provided in the wall of vessel24 within the extent of the stroke of said piston so that a charge ofthe solid particleliquid mixture will be fed to the advancing face ofsaid piston prior to the movement of said piston to advance theparticles (Fig. 2), the piston passing said opening 25 about midway ofits stroke to compact and advance the solid particles in the vessel, thevalve 18 then operating to cut off the feed of the solid particle-liquidmixture into the, vessel and recharge said valve with chips, the liquidremaining in the bore 20 of said valve passing through screen 22 toexhaust pipe 21 to be collected for return to tank. 12 if desired (Fig.3).

The lower end of shaft 30 extends into a hydraulic cylinder 40 mountedbeneath the lower end of reaction vessel 24 and forms the pistonthereof, said cylinder 46 being provided with an inlet pipe 42 connectedto a suitable source of fluid pressure, (not shown) through valve 44 toraise said shaft with the plate 32 to reciprocate said plate, the forceof the vessel pressure against the area of the upper end of said shaftbeing great enough to rapidly lower the plate 32 when the pressure incylinder 40 is exhausted, the pressure vessel 24 in such circumstancesacting as an accumulator to provide the necessary force at a rapid rate.Furthermore, the volume of liquid displaced by shaft 30 varies as theshaft reciprocates, causing the entire volume of liquid in vessel 24 toreciprocate over a limited distance. Means including a double actingsolenoid 46 operated by switches 47 and 48 actuated by lugs 36 on piston30 are provided for alternately connecting pipe 42 to its source ofpressure and to exhaust and to reciprocate plate 32 through apredeterminde stroke at any desired rate. A similar solenoid 50 operatedby a double throw switch 52 positioned to be operated by lugs 36 at thelower end of the piston stroke is provided for rotating valve 18 to feeda solid particleliquid mixture charge into vessel 24 when said piston isat the lower end of its stroke. If desired, the piston face plate 32 maybe provided with short upstanding radially extending fins and the pistonmay be rotated to aid in distributing the infed chips by, in effect,stirring the liquid at the lower end of vessel 24.

in operation, the solid particle-liquid mixture or slurry of chips andliquid is fed into the reaction vessel 24 by centrifugal pump 16 andvalve 18 so that it will be pressurized before entering said vessel,such feeding taking place in timed relation to the piston, i. e., whenthe piston is in the lower extent of its stroke. The reciprocation ofplate 32 for a short distance axially of the vessel 24 at a rate of say12 strokes per minute serves to provide an axial component of movementof the chips fed through aperture 25 to move them successively upwardlyto the bottom of the mass of chips in the reaction vessel and compactthem thereon and advance them therethrough by exerting force onlyagainst the chips at the bottom end of said mass or zone. Furthermore,since the mass of chips fills the reaction vessel and its bottom extendsdownwardly toward the plate, such reciprocatory movement acts on thebottom of said mass of chips to advance it upwardly at a desired uniformaverage rate as Well as to compact it. The taper of the vessel makes itpossible for the plate 32 to move the mass of chips upwardly withoutexerting extraordinarily high pressures on the chips, as too highpressures seriously damage the chips and cause a substantial reductionin the quality of the resulting pulp. The digested chips are dischargedas pulp through mechanism 26. During a run, the reaction vessel is keptfull of chips to maintain a compacted elongated mass or zone thereof,the individual chips moving slowly upwardly as they are reduced to pulpand discharged through mechanism 26 at the top of the reaction vessel.

Since the liquid component of the mixture passes freely through theperforations 34 in plate 32 during such reciprocation, the reciprocatorymovement will not aifect the movement of the liquid so that the chipsmay be advanced independently thereof, except for the limitedreciprocatory movement of the liquid caused by the reciprocation ofshaft 30, which limited movement is valuable in that it aids thereaction by continuously washing away from the chips the materialdissolved by the liquid chemical solution. Furthermore, the liquid maybe continuously recirculated for'heating or the like through filter 28and outlet 29.

The upward movement of plate 32 due to the pressure in hydrauliccylinder 40 is relatively slow, occupying say of the total cycle, whilethe downward movement due to the pressure of the vessel acting on theend of shaft 30 is much more rapid, occupying but about 10% of thecycle. This is made possible by using the vessel in effect as ahydraulic accumulator. Such rapid downward movement forces the liquidunder plate 32 to move rapidly through the perforations 34, thusflushing away any solid particles that may have become lodged in theperforations 34.

Thus it will be seen that we have provided a novel means for advancingthe solid particle component of a practical upflow continuous pulpingapparatus for wood chips or other fibrous materials, or a countercurrentwashing apparatus for such materials as by introducing washing liquid atthe upper filter section 28 and removing it from outlet 29, and in suchcase pressure operation may not be necessary. Various modifications ofthe invention within the spirit thereof and the scope of the appendedclaims will occur to those skilled in this art.

We claim:

1. In apparatus for the continuous treatment of the solid particlecomponent of a solid-particle-liquid mixture in an upwardly arrangedelongated reaction vessel having a generally uniform cross-sectionalarea at least not decreasing in its upward direction by feedingsubstantially continuously said mixture into said reaction vesselthrough an opening in the side wall adjacent the lower end thereof tomaintain a compacted mass of said solid particles within an elongatedzone in the central and opposite upper end portions thereof, advancingthe solid particle component thereof upwardly through said zone at arate substantially independent of the movement of liquid in said vesselto treat said solid particles, meanwhile treating the same, andsubstantially continuously discharging said treated solid particles fromsaid opposite upper end of said vessel, the improvement comprisingforaminous piston means mounted adjacent the lower end of said vesselfor generally vertical reciprocatory movement and extending generally ina horizontal plane across substantially the entire cross-sectional areaadjacent said lower end of said vessel with its outer periphery closelyadjacent the inner walls of said vessel for free passage of said liquidtherethrough while preventing passage of said solid particles, means forreciprocating said piston means through a predetermined stroke, andmeans operated in timed relation to said piston means for feeding saidsolid particle component into said vessel adjacent to and in advance ofsaid piston means through an opening positioned in the side wall of saidvessel within the extent of the stroke of said piston means to advancesaid solid particles into contact with solid particles at the lower endof said zone and to exert lifting force directly only on particleslocated at the entrance end of said zone to progressively compact saidparticles and to advance the mass of said particles progressivelyupwardly through said zone while permitting free movement of liquidthrough said piston means.

2. In apparatus for the continuous treatment of the solid particlecomponent of a solid particle liquid mixture in an elongated, generallyupright reaction vessel of generally uniform and gradually increasingcross-sectional area throughout the major portion of its length at leastnot decreasing in cross-sectional area in its upward direction byfeeding substantially continuously said mixture into said reactionvessel through an opening in the side wall adjacent the lower endthereof to maintain a compacted mass of said solid particles within anelongated zone in the central and upper portion thereof filling itsentire cross-sectional area, advancing the solid particle componentthereof upwardly through said zone at a rate substantially independentof the movement of liquid in said vessel to treat said solid particles,meanwhile treating the same, and substantially continuously dischargingsaid treated solid particles from the upper end of said vessel, theimprovement comprising foraminous piston means mounted adjacent thelower end of said vessel for generally vertical reciprocatory movementand extending generally in a horizontal plane across substantially theentire cross-sectional area of said vessel with its outer peripheryclosely adjacent the inner walls of said vessel for free passage of saidliquid therethrough while preventing passage of said solid particles,means for reciprocating said piston means through a predeterminedstroke, means for feeding solid particle liquid mixture into said vesseladjacent to and in advance of said piston means through an opening inthe side wall of said vessel within the extent of the stroke of saidpiston means including valve means operating in timed relationship tosaid piston means for receiving in a first position a charge of solidparticles and in a second position a charge of liquid for dischargingsaid solid particles and liquid into said vessel prior to movement ofsaid piston means to advance said solid particles into contact withsolid particles at the lower end of said zone and to exert lifting forcedirectly only on particles located at the entrance end of said zone toprogressively compact said solid particles at the lower end of said zoneand to advance the mass of solid particles progressively upwardlythroughout the length of said zone while permitting free movement ofliquid through said piston means, and discharge means for dischargingthe treated solid particles from the upper end of said zone at the upperend of said reaction vessel.

References Cited in the file of this patent UNITED STATES PATENTS1,982,130 Wollenberg Nov. 27, 1934 1,991,244 De La Roza Feb. 12, 19352,038,721 Desmond Apr. 28, 1936 2,359,543 Branzell et al Oct. 3, 19442,383,684 Richter Aug. 28, 1945 2,709,652 Plunguian May 31, 19522,680,683 Obenshain June 8, 1954

1. IN APPARATUS FOR THE CONTINUOUS TREATMENT OF THE SOLID PARTICLECOMPONENT OF A SOLID-PARTICLE-LIQUID MIXTURE IN AN UPWARDLY ARRANGEDELONGATED REACTION VESSEL HAVING A GENERALLY UNIFORM CROSS-SECTIONALAREA AT LEAST NOT DECREASING IN ITS UPWARD DIRECTION BY FEEDINGSUBSTANTIALLY CONTINUOUSLY SAID MIXTURE INTO SAID REACTION VESSELTHROUGH AN OPENING IN THE SIDE WALL ADJACENT THE LOWER END THEREOF TOMAINTAIN A COMPACTED MASS OF SAID SOLID PARTICLES WITHIN AN ELOGATEDZONE IN THE CENTAL AND OPPOSITE UPPER END PORTIONS THEREOF, ADVANCINGTHE SOLID PARTICLE COMPONENT THEREOF UPWARDLY THROUGH SAID ZONE AT ARATE SUBSTANTIALLY INDEPENDENT OF THE MOVEMENT OF LIQUID IN SAID VESSELTO TREAT SAID SOLID PARTICLES, MEANWHILE TREATING THE SAME, ANDSUBSTANTIALLY CONTINUOUSLY DISCHARGING SAID TREATED SOLID PARTAICLESFROM SAID OPPOSITE UPPER END OF SAID VESSEL, THE IMPROVEMENT COMPRISINGFORAMINOUS PISTON MEANS MOUNTED ADJACENT THE LOWER END OF SAID VESSELFOR GENERALLY VERTICAL RECIPROCATORY MOVEMENT AND EXTENDING GENERALLY INA HORIZONTAL PLANE ACROSS SUBSTANTIALLY THE ENTIRE CROSS-SECTIONAL AREAADJACENT SAID LOWER END OF SAID VESSEL WITH ITS OUTER PERIPHERY CLOSELYADJACENT THE INNER WALLS OF SAID VESSEL FOR FREE PASSAGE OF SAID LIQUIDTHERETHROUGH WHILE PREVENTING PASSAGE OF SAID PARTICLES, MEANS FORRECIPROCATING SAID PISTON MEANS THROUGH A PREDETERMINED STROKE, ANDMEANS OPERATED IN TIMED RELATION TO SAID MEANS FOR FEEDING SAID SOLIDPARTICLES COMPONENT INTO SAID VESSEL ADJACENT TO AND IN ADVANCE OF SAIDPISTON MEANS THROUGH AN OPENING POSITIONED IN THE SIDE WALL OF SAIDVESSEL WITHIN THE EXTENT OF THE STROKE OF SAID PISTON MEANS TO ADVANCESAID SOLID PARTICLES INTO CONTACT WITH SOLID PARTICLES AT THE LOWER ENDOF SAID ZONE AND TO EXERT LIFTING FORCE DIRECTLY ONLY ON PARTICLESLOCATED AT THE ENTRANCE END OF SAID ZONE TO PROGRESSIVELY COMPACT SAIDPARTICLES AND TO ADVANCE THE MASS OF SAID PARTICLES PROGRESSIVLEYUPWARDLY THROUGH SAID ZONE WHILE PERMITTING FREE MOVEMENT OF LIQUIDTHROUGH SAID PISTON MEANS.